1. Field of the Invention
The present invention relates to a hollow blade for a turbomachine, especially a large chord fan blade.
The advantages of using large chord blades in turbomachines are known, particularly in the case of the fan rotor blades in a bypass turbojet engine. These blades must cope with severe operating conditions, and, in particular, must possess mechanical properties giving adequate anti-vibration characteristics and resistance to impact by foreign bodies. The aim of achieving adequate speeds at the tips of the blades has also led to research into reducing the masses of the blades. This has resulted in the use of hollow blades.
2. Description of the Prior Art
French Patent No. 1 577 388 discloses one example of a hollow blade in which the blade is made up of two wall elements between which a honeycomb structure is arranged, the wall elements being made of a titanium alloy and being formed to the desired profile and shape by hot pressing.
U.S. Pat. No. 3 628 226 describes a method of manufacturing a hollow compressor blade involving a metal bonding by diffusion welding of two elements or half-blades having a flat grooved assembly surface.
Other known techniques for obtaining hollow blades, particularly for the fans of turbojet engines, combine operations or pressurized metal diffusion welding and pressurized gas superplastic forming. One example of this technique is disclosed in U.S. Pat. No. 4 882 823.